hash table in c#

Yes. And addition with cast

That's the same thing. Only added 200 to the original value :)

It should be: hashtable["IL"]=Convert.ToInt32(hashtable["IL"])+200; I think.

I'm sorry I gave you a terribly wrong answer in my first post :( It can be done ^_^ When you have assigned the value to the key: hashtable.Add("IL" ,500); You can change the value like: hashtable["IL"] = 700; This should solve your problem. (Sorry for the incorrect post)

first using hash table can u tell me how delete the the entry from the hash table for example Hashtable H = new Hashtable(); H.Add("IL", 500); //want to delete this entry, and add a new entry with the same key as H.Add("IL", 700); will it work H.Delete("IL",500);

hashtables are not designed to change the values of keys. It's for easy store/retrieve functionality. But you could remove the key first and then add it again with the new value